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CHP just keeps on running

The small-scale combined heat and power (CHP) market has been setting the pace in the energy saving challenge for the past few years and that is clearly set to continue, says David Shaw
Government figures published last year showed that year-on-year growth in the CHP market remained around 20 per cent, and the increase in CHP had cut the country's CO2 emissions by a further one million tonnes in the previous year. Cogeneration is a highly efficient process that produces both power and heat simultaneously; typically converting as much as 80 per cent of input fuel into useful energy and reducing carbon emissions by up to 30 per cent.

The small-scale CHP sector - below 50 kWe - has grown to over 400 MW of capacity and the technology, as a whole, provides 7.5 per cent of the UK's electricity requirements and saves 14 million tonnes of CO2 per year. Small scale systems have done particularly well during the recession because they are seen as the most cost effective and easy way for many building refurbishment projects to meet carbon reduction targets imposed by local planning authorities.

Significant savings possible
A particularly impressive examle of the significant savings made possible by the application of small-scale CHP technology is the experience of the London Fire Brigade (LFB). The world's third largest firefighting organization, managed by the London Fire and Emergency Planning Authority (LFEPA) which is part of the Greater London Authority (GLA) faced a challenge from the London Mayor to reduce energy consumption by 15 per cent by 2010.

As a major energy consumer, the principal focus of the Brigade was to reduce its reliance on mains energy. As the LFB energy and compliance manager Lloyd Bentley explained, 'Buying electricity from the Grid is expensive and we are subject to the Carbon Tax at £12 per tonne of emissions. It makes sense for us to get as much as we can from sustainable sources close to the point of use.'

CHP was of considerable interest. A series of Carbon Trust field trials had concluded that 'a mini-CHP unit can provide savings of between 15 and 20 per cent when applied as the lead boiler'. This technology works best in applications with high and continuous heating loads, because the longer the system is running the more efficient it is. Ideally, it should run for at least 4,000 hours a year, making it suitable for hospitals, leisure centres, sheltered accommodation, homes with swimming pools - and fire stations.

As Mr. Bentley commented, 'CHP is the most appropriate technology for our energy intensive 24/7 buildings. It is 'easy fit' and offers the bonus of free electricity. Consequently, it is our core technology for reducing the carbon impact of electricity and hot water across our estate.'

With this decision made, the LFB undertook an ambitious programme of energy upgrades involving Dachs mini-CHP and photovoltaic (PV) panel arrays with improved controls via Building Management Systems (BMS), widespread replacement of conventional lighting with LEDs and upgrades to window glazing. Currently, the stations get 6 per cent of their total electricity supply from renewables and LFB is intent on doubling its renewables capacity with mini-CHP as the lead technology. It has an ongoing target of a 3 per cent cut in energy use every year. Over a six year period, the Brigade has seen its carbon footprint shrink by 28 per cent with a major contribution from its mini-CHP installations, of which there are 41 across its estates providing heating, hot water and electricity.

Small-scale applications are not the only CHP success story. The most recent DECC (Department of Energy and Climate Change) statistics show that there are over 1,900 CHP schemes currently operating in the UK. For example, a District Heating (DH) scheme, providing heat from a central source, can cover a number of buildings ranging from single figures to many hundreds and statistics indicate that some 80 DH networks are already established in the UK. Whilst natural
gas is by far the major fuel type used by CHP schemes, 8 per cent of the fuel used is from renewable sources.

Government policy is to encourage the growth of CHP schemes, by a mixture of exemptions, concessions and incentives. For example, the Carbon Reduction Commitment (CRC) requires businesses covered by this measure to purchase allowances to cover the CO2 emissions from all fixed-point energy sources. However, in the case of a CHP installation, allowance will only need to be purchased in relation to the electricity consumed on site, meaning that no allowances have to be purchased to cover heat from CHP.

There are reported to be some 1,000 individual buildings in the UK that utilise both heat and power generated by a CHP source, with a significant potential market identified for small-scale CHP in non-domestic buildings.

Reducing harmful emissions
This should be of great interest to both public and commercial undertakings, with the LFB bearing witness to the effectiveness of such installations, both in terms of reduced harmful emissions and savings in fuel bills. In just four months, the LBF fire station at Battersea received 4,100 kW of electricity from the operation of its mini-CHP unit, which, together with savings derived from photovoltaic renewable energy equipment, yielded an annual saving of £2,500 on fuel costs.

This means that the payback on the purchase cost of the mini-CHP system could be less than six years. One further observation from Mr Bentley, previously identified, should be noted. 'Contractors need more experience in the installation, commissioning and maintenance of many low carbon technologies. The products are coming through well, but there are still a lot of lessons to be learned by contractors about how to get them to deliver their full potential.' The significance of this will not be lost on heating industry professionals.

This is just one example of the high performance levels that, in the right location, can be achieved by the use of CHP technology. Suitable for a wide variety of buildings, CHP is proving to be a significant contributor towards enabling commercial undertakings to comply with environmental policies that support long-term energy efficiency goals, whilst countering the high cost to energy users of their implementation.

// The author is LZC national sales manager of Baxi Commercial, responsible for
Baxi-SenerTec UK Dachs mini-CHP
//
10 September 2013

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